Web transport

ABSTRACT

A web transport by which a thin strip or web of material is driven by a novel roller having inclined confronting faces which grip the web by the extreme edges, avoiding any wear or damage to the web faces. In one form the drive returns the web in the general direction of the supply and permits slippage when the web from the supply is slack, but grips for a positive drive upon slight tension in the web supply. In another form, essentially positive drive is obtained at all times in a straight through configuration, both forms being adaptable to film, tape and other strip elements.

United States Patent Isbell [4 1 Apr. 25, 1972 [54] WEB TRANSPORT [2i] Appl. No.: 45,412

US. Cl. ..226/l84, 226/ I90 Field ol Search .226/184, I90, I82, I9I 79, 226/I96, I99, H8, I19, I68, I83; 242/550]; 27I/49, 52; 741230.0I. 230.17 A

Jensen ..242/55.0I Staklinski ..226/79 Primary Examiner-Allen N. Knowles Assistant Examiner-Gene A. Church Attorney-Carl R. Brown [57] ABSTRACT A web transport by which a thin strip or web of material is driven by a novel roller having inclined confronting faces which grip the web by the extreme edges, avoiding any wear or damage to the web faces. In one form the drive returns the web in the general direction ofthe supply and permits slippage when the web from the supply is slack, but grips for a positive drive upon slight tension in the web supply. In another form. essentially positive drive is obtained at all times in a straight through configuration, both forms being adaptable to film, tape and other strip elements.

4 Claims, 5 Drawing Figures TAKE-UP PATENTEDmzs m2 //l ////1 ////)(/////1/ 2s 30 2e Qki Fig. 3

INVENTOR.

WILLARD D. ISBELL ATTORNEY was TRANSPORT BACKGROUND OF THE INVENTION The term web transport includes the driving of photo graphic film, punched or magnetic tape, plastic or metal strips in manufacturing processes, and various other applications in which an elongated strip or web is driven. When surface wear is not unduly critical. conventional pressure rollers may be used to grip the web but for many purposes, gripping must be limited to the web edges. For photographic film, undercut or concave rollers have been used, the edge portions only of the film being engaged by narrow shoulders of the rollers. With pressure roller drive, a certain minimum contact area must be retained for proper driving grip, but even this may be undesirable in some instances.

SUMMARY OF THE INVENTION The web transport described herein drives by gripping the web by the extreme edges, with no face contact on either face of the web. A special drive pulley has a circumferential channel with opposed side walls which are slightly inclined to a plane perpendicular to the axis of rotation, the web seating into the channel until gripped between the inclined faces. With respect to the flat rectangular cross section of the web, the grip is actually at the corners of the side facing the pulley. In one form the web wraps around the pulley for more than I80, which provides a positive drive when there is a slight tension in the web supply, but allows the drive to slip when the supply is slack.

In another form the drive is essentially straight through, the web seating into the pulley for only a few degrees of peripheral contact and being held by a concave retaining roller. The concave roller avoids any face contact with the web and does not provide any actual driving pressure, the drive still being the frictional edge contact with the pulley. The latter form is particularly suitable for incremental drive. Either form is adaptable to film, tape, metal strip, or other-web material having sufficient inherent stiffness across its width to permit the edge gripping drive without bowing or collapsing to the point of slippage.

The primary object of this invention, therefore, is to provide a new and improved web transport.

Another object of this invention is to provide a new and improved web transport in which the web is gripped only by the extreme edges between opposed faces of a driving pulley.

A further object of this invention is to provide a new and im proved web transport which is adaptable to return path or straight through configuration of the web, with continuous or incremental drive.

Other objects and many advantages of this invention will become more apparent upon a reading of the following detailed description and an examination of the drawings wherein like reference numerals designate like parts throughout and in which:

FIG. I is a side elevation view of the return path configuration ofthe transport mechanism.

FIG. 2 is a sectional view taken on ine 2-2 of FIG. 1.

FIG. 3 is an enlargement of a portion of FIG. 2.

FIG. 4 is a side elevation view of the straight through form of the drive.

FIG. Sis a sectional view taken on line 5-5 of FIG. 4.

DESCRIPTION OF THE PREFERRED EMBODIMENT In the return path form of the drive shown in FIGS. [-3, a drive pulley I is secured to a shaft I2, which is journalled in a bearing [4 on a support member 16. No means is shown for driving shaft 12, since the structure is adaptable to many different transport arrangements, and support member 16 can be a portion of the associated structure.

Drive pulley II) has a shallow circumferential channel 18, with opposed side walls 20 and 22 which are inclined at a shallow, inwardly divergent angle relative to a plane perpendicular to the axis of rotation, so that the width of the channel decreases inwardly. The actual angle of inclination which has been found particularly effective is on the order of 9 or l0, but may vary to suit particular web configurations.

The drive pulley is dimensioned to suit the width of the web to be driven. As shown'in FIG. 3, the web 24 seats into channel 18 so that the corners 26 and 28 of the web engage inclined walls 20 and 22, respectively, when the web is still clear of the bottom of the channel. The outer width of the channel is thus greater than the width of the web and the inner or base width of the channel is narrower than the web. Under driving tension a slight inward bowing of the web may occur, but the inner face 30 of the web does not touch the pulley. The only contact of the web on the pulley is at the extreme edges or comers 26 and 28. It is this type of gripping action which necessitates a certain inherent stiffness across the width of the web, to avoid bowing beyond a frictional driving engagement. The thinner types of magnetic tape may not have sufi'icient stiffness, but thicker tapes, motion picture films, punched tapes, metal strips and the like usually have the required properties.

Frictional driving engagement is obtained by wrapping the web 24 around pulley 10 for slightly more than I of peripheral contact, resulting in the return or take-up portion 32 of the web returning toward the direction of the supply portion 34. To ensure that the egress tangent point 36 of the web from pulley 10 is more than l80 from the ingress tangent point 38, as indicated in FIG. I, the take-up portion 32 is passed over a retaining roller 40 freely rotatably mounted on a bearing 42 on support member 16. The retaining roller 40 is spaced from the pulley to guide the take-up portion of the web and has a concave face 44 to avoid surface contact with the web. While there may be a very small contact with the web at the outer ends of the roller, as seen in FIG. 2, this is minimized as musch as possible, and is certainly insufficient for frictional driving engagement. Roller 40 merely holds the web in proper wrap around position on the pulley and does not contribute to the driving force.

With the greater than I80 ofwrap around, the driving contact pressure is quite small. As long as there is some tension in the web supply, the pressure is sufficient for positive drive. However, when web supply goes slack, the drive will slip. In continuous operation this provides a substantially constant speed in the take-up portion of the web regardless of the supply, and avoids over-running when the web slackens due to excess supply.

An alternative drive arrangement providing a straight through passage of the web is shown in FIGS. 4 and 5. in this configuration the same drive pulley I0, shaft [2 and bearing 14 are used, on a support member 46 adapted to the modified form. A web 24 passes through the top portion of pulley l0, seating in channel 18 and being gripped at the corners as described above. For driving engagement the web is held in the channel by a retaining roller 48 freely rotatably mounted on bearings 50 on a shaft 52 secured to support member 46. The retaining roller is positioned just beyond the tangent point 54 of the web with the pulley, so that the web has a short peripheral wrap around on the pulley. As shown, the retaining roller has an angular displacement of about l5 from the tangent point, but this can vary to some extent.

The length of the retaining roller 48 is closely equal to the width of web 24, so that the roller seats down into channel 18 and holds the web in contact with the inclined faces 22 and 24, the roller having a concave face 56 to avoid contact with the web. It should be understood that the retaining roller 48 does not apply a driving pressure, but merely holds the web with sufficient wrap around for pulley 10 to have frictional driving engagement. With the web held in a constant position, the mechanism of FIGS 4 and 5 provides a more positive drive than the form of FIGS. l and 2, which allows slippage. For this reason the straight through drive is particularly suitable for incremental drive as well as continuous motion. However, by careful positioning of the retaining roller, the drive can be designed to have a controlled slippage, if necessary, to avoid breakage of the web in intermittent operation.

In either form the extreme edge drive avoids damage to the web, which is important when handling photographic film. The technique is also particularly efiective in moving highly finished or specially treated metal or plastic strip in certain manufacturing processes. Material, size, proportions and mountings of the pulleys and rollers are readily adapted to suit specific uses.

Having described my invention, I now claim.

1. A web transport for driving an elongated web of thin flat material having a rectangular cross section, comprising:

a support member;

a driven pulley mounted on said support member, said pulley having a circumferential channel with inclined opposed side walls in fixed relation tapering from an outer width greater than the width of the web, to an inner width less than that of the web, the web seating between the inclined walls clear of the base of the channel and being gripped only at the inside comers of the extreme edges;

and a freely rotatable retaining roller mounted on said support member in a fixed position adjacent said driven-pulley, for holding the web in a predetermined wrap around configuration on the pulley, said retaining roller having a concave face and contacting the web only at the extreme edges.

2. A web transport according to claim 1, wherein the angle of inclination of said side walls is on the order of 10 relative to a plane perpendicular to the axis of rotation of the pulley.

3. A web transport according to claim I, wherein the peripheral wrap around of the web is in excess of I", and said retaining roller is spaced from said pulley adjacent the egress point of the web therefrom.

4. A web transport according to claim 1, wherein the peripheral wrap around of the web is on the order of IS", and said retaining roller is inset into said channel in edge contact with the web. 

1. A web transport for driving an elongated web of thin flat material having a rectangular cross section, comprising: a support member; a driven pulley mounted on said support member, said pulley having a circumferential channel with inclined opposed side walls in fixed relation tapering from an outer width greater than the width of the web, to an inner width less than that of the web, the web seating between the inclined walls clear of the base of the channel and being gripped only at the inside corners of the extreme edges; and a freely rotatable retaining roller mounted on said support member in a fixed position adjacent said driven pulley, for holding the web in a predetermined wrap around configuration on the pulley, said retaining roller having a concave face and contacting the web only at the extreme edges.
 2. A web transport according to claim 1, wherein the angle of inclination of said side walls is on the order of 10* relative to a plane perpendicular to the axis of rotation of the pulley.
 3. A web transport according to claim 1, wherein the peripheral wrap around of the web is in excess of 180*, and said retaining roller is spaced from said pulley adjacent the egress point of the web therefrom.
 4. A web transport according to claim 1, wherein the peripheral wrap around of the web is on the order of 15*, and said retaining roller is inset into said channel in edge contact with the web. 